1. Field of the Invention:
The present invention relates to an improvement in document feeding device for use with a recording apparatus such as an electrophotographic reproducing machine and a reading machine for reading document by the exposure etc.
2. DescriptIon of the Prior Art:
As an apparatus which can supply documents to be reproduced to the recording apparatus efficiently and even in an unmanned state, automatic document feeders (ADF) have already been proposed. However, in the past, the function of the apparatus has been mainly limited to the reproduction of only one side of the document
On the other hand, the necessity of ADF capable of reproducing dual-surface documents by development of the recording apparatus capable of continuously reproducing the inside and outside (two sides) of a sheet of recording paper have been recently increased, and many attempts have been proposed to provide a mechanism of reversing the inside and outside of a document within ADF. Proposals of these are disclosed in Japanese Patent Laid-Open Nos. 216159/1984 and 112738/1978, Japanese Utility Model Laid-Open No. 4548/1984, Japanese Patent Laid-Open Nos. 8834/85 and 26559/85, and the like.
These document feeding devices each comprise a document supply portion for supplying documents stacked on a document supply tray one by one to the recording apparatus, a document feeding portion adapted to stop the feed at an exposure position, a document reversing portion for reversing the inside and outside of a document one surface of which has been exposed to again feed it to the recording apparatus, and a document ejecting portion for ejecting a document the other surface of which has been exposed to a document ejecting tray. In many examples of the document feeding devices, feeding rollers disposed in these portions are driven as a whole by means of two driving motors, one for a reversible motor and the other for a uni-directional motor, in terms of a mechanism of the apparatus.
Namely, two kinds of these driving motors are necessary, one which can be switched to normal and reverse modes since the document one surface of which has been exposed in the document feeding portion has to be reversely fed to the reversing portion as is known, and the other which supplies power to the feeding rollers in the document supply portion, document reversing portion and document ejecting portion, which need be rotated only in one direction.
Furthermore, the motors are expensive, and need be synchronized. Therefore, in the case where the whole structure is driven by one kind of motor, it is necessary, for example, to obtain a driving force rotating in one direction from a reversible motor. As in a prior art example shown in FIG. 8, it becomes necessary to have the function wherein a driving device comprising at least five gears GO1, GO2, . . . GO5 and two electromagnetic clutches CL1, CL2 is provided whereby the electromagnetic clutches are actuated in response to timing of normal and reverse rotation of a driving motor M so that the rotation of a driving output may be always defined in one direction.
Alternatively, the reversible output may be obtained by means of a unidirectional driving motor in place of the aforementioned reversible driving motor but under the actual condition, the driving device having the aforementioned scale and function is necessary and in any method, a great burden is imposed on the price of the apparatus.
Moreover, since the above-described proposed ADFs employ a mechanism in which the document passes a plurality of paper passages in reversing the inside and outside of the document the surface of which has been exposed to again expose the inside, the feeding mechanism becomes complicated. In addition, the feeding rollers need be frequently switched to normal and reverse modes and driven, and besides, many paper supply/ejection switching members have to be provided on the paper passages, which lead to increasing the size of apparatus and complicating he apparatus, thus increasing the cost.
In addition, according to these proposals, documents are fed to a document reversing portion comprising a loop-like feeding passage to circulate the documents thereby reversing the inside and outside. However, since generally, the length of the feeding passage is formed to be further longer than the longest document to be used, the document reversing portion becomes relatively bulky.
However, as in the proposal in the aforementioned Japanese Utility Model Laid-Open No. 4548/1984, the feeding of documents in the document reversing portion is accomplished by sandwiching the document between a large-diameter driving roller arranged in the central portion of the aforementioned feeding passage and a plurality of pressing rollers in pressure contact with the peripheral surface of the first-mentioned roller and rotating following said driving roller, and therefore, a space portion within the document reversing portion is almost occupied by the driving roller to fail to utilize it for accommodation of other mechanism members.
Furthermore, in the ADF which can copy the inside and outside of such documents, it is necessary to drive many groups of feeding rollers in an attempt of not only delivering and feeding documents but reversing the inside and outside of documents, the ADF is controlled so as to be normally rotated, reversely rotated and stopped by signals from a control portion within the apparatus or the recording apparatus body according to the status of the document feeding by means of a large and powerful driving motor housed therein. However, in most of conventional ADFs, the driving motor cannot be accommodated within the space of the document feeding system in view of the mechanism thereof, and thus the motor had to be accommodated in a space particularly provided outside the feeding system.
This tends to increase the volume of ADF and to an unsuitable position of center of gravity, deteriorating the handling properties.
Moreover, in the document feeding device as described above, when a document surface of which has been exposed is reversed in inside and outside, the document is fed reversely to the original feeding passage, and then the document is guided to the reversing portion halfway of the feeding passage to effect the reversal of the inside and outside of the document.
FIG. 9 shows an example of such feeding passage. The document is first fed by a paper supply roller from the direction indicated by arrow A into a U-shaped guide portion 125a, the document with the surface thereof directed downwardly is then moved onto a platen glass 111 and fed to a predetermined exposure position by means of a feeding belt 130 which is rotating clockwise.
The document the surface of which has been exposed is reversely fed in the direction as indicated by arrow B by means of the feeding belt 130 which has been reversed to the counterclockwise rotation and delivered into a document reversing portion 125b. In this case, movable guide members 127 have to be provided at an outlet of the guide portion 125a and at a branched portion 127a of an inlet of the reversing portion 125b.
The movable guide member 127 used herein comprises a device in which generally, an elongated metal or resin plate is rotatably supported at both ends so that it may be switched to a position as indicated by the illustrated solid line or broken line by means of a power source such as a solenoid in response to the feeding direction of the document.
More specifically, where the document is reversely fed in the direction as indicated by arrow B as previously mentioned, the movable guide member 127 at the position as indicated at the solid line closes the outlet of the guide portion 125a to prevent the reverse movement relative to the guide portion 125a. On the other hand, where the document is moved about the reversing portion 125b and again fed from the direction indicated by arrow C onto the platen glass 111, and, where the document is fed from the direction indicated by arrow A as previously mentioned, it rotates to the position indicated by the broken line to open the outlet of the guide portion 125a.
However, such movable guide member 127 itself becomes large-sized, and the supporting construction thereof becomes somewhat complicated. In addition, it is necessary to control operating timing with respect to the power source A plurality of such members need be provided according to the feeding mechanism, which cannot be ignored in terms of space as well as cost.